Sunday, July 29, 2007
P3

Kinetic Model of Lipase-catalyzed Asymmetric Alcoholysis of &alpha-Cyano-3-Phenoxybenzyl Acetate in Organic Media

Jianping Wu1, Fei Yu2, Lirong Yang1, and Roger Ruan2. (1) Department of Chemical and Biochemical engineering, Zhejiang University, Zheda Road 38, Hangzhou, China, (2) Department of Bioproducts and Biosystems Engineering, University of Minnesota, 1390 Eckles Ave, Saint paul, MN 55108

The synthesis of optically pure cyanohydrins is an area of growing interest in synthetic chemistry. a-cyano-3-phenoxybenzyl alcohol(CPBA) is one of the most important cyanohydrins. Transformation of the nitrile group of optically pure S-CPBA provides optically active a-hydroxycarboxylic acid, aldehyde, and ketone, as well as 2-amino alcohol, therefore optically pure cyanohydrins and their derivatives are important building blocks for the production of pharmaceuticals and agrochemicals. Some examples of the synthesis of CPBA and its resolution had been reported. Among them, due to  the advancement in technology of enzyme-catalyzed reaction in organic media, the synthesis of S-CPBA by lipase-catalyzed asymmetric alcoholysis of a-cyano-3-phenoxybenzyl acetate(CPBAc) in organic media was the most attractive one.  The effects of the enzyme, solvent, alcohol, water content and so on were investigated carefully in previously study. The kinetic characteristics of the lipase-catalyzed asymmetric alcoholysis of a-cyano-3-phenoxybenzyl acetate in organic media were studied here. A ping-pong bi-bi mechanism with competitive inhibition by alcohols was proposed. And a kinetic model was established on the base of this mechanism. The complete rate equation for this mechanism was derived from the diagrams of King and Altman. Then the kinetics mechanism was applied to the reversible reaction system. The model parameters were simulated from the experimental data. The calculation results showed that he model simulation curves were in good agreement with the experimental data of different substrate concentrations at the beginning of reaction.

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